UBS transmission lines are more and more popular since more and more electronic devices use UBS connectors for data communication. However, it induces a problem of storage of USB transmission lines. The prior art wire-winding devices have two problems. One is that the positioning unit of the wire-winding device has a rolling ball movable in a guide groove of a rotary disk for rotating and positioning the wire-winding device. However, the rolling ball is very small. It is easily to separate from the guide groove due to collision so as to destroy the wire-winding device. The other problem is that a center of a lower cover of the wire-winding device has a post which is formed by two semi-round rods. A center thereof is locked by a screw and a lateral notch thereof is embedded by a spiral spring. When the screw is locked into the post, the two semi-round rods are possible to be expanded. After using a long time, the ends of the spiral spring will separate from the notch so that the wire-winding device is destroyed.
Moreover, the prior art is not suitable to be carried outdoors. Further, the transmission line is too long to be wound conveniently and easily. Thereby, the transmission line will interact by itself so as to form many joints. When it is desired to use the UBS transmission lines, the user must take a longer time to release the wire-winding device.